Mechanisms of layer growth in microwave-PECVD silan plasmas – Experiment and simulation

For the specific manipulation of barrier-layer properties, a detailed analysis of the layer-growth mechanisms in microwave-PECVD was carried out for Si-wafers with a trench structure as ”model cavities” in the μmμm range. The deposition of a-Si:H (hydrogenated amorphous silicon) layers in pure monosilane plasmas was used as model system to compare experimental results and simulations using the 2D binary collision code SDTrimSP-2D, which showed very good agreement with the experiment. Without bias the layer tends to close above the cavities from both sides, but cracks remain at the closure positions. By biasing the substrate a smoothing of the layer edges above the cavities occurred. Thus, the cavities remained open for a longer time and a more homogeneous coating of the notches is obtained.